NO. 1 BARNARD : AMPHIPODA OF THE FAMILY AMPELISCIDAE 31 



(1), 481-35 (4), 564-36 (5), 576-36 (1), 706-37 (2), 726-37 (1), 

 745-37 (5), 856-38 (1), 1075-40 (4), 1714-49 (2), 1757-49 (1), 

 1965-50 (2). 



Remarks: This species is very closely related to Ampelisca cristata 

 forma microdentata, new form, differing essentially only in the shape of 

 the dorsal crest of pleon segment 4. Slight intergradations between the 

 two species have been found in the material at hand, but in all cases 

 A. cristoides is easily separated from A. cristata forma microdentata (see 

 remarks under latter) . Whether A. cristoides is only a form of A. cristata 

 or whether it is indeed a reproductively isolated population cannot be 

 decided at this time. It has been given specific status to facilitate the 

 future work of taxonomists. 



Distribution : Along the coast of Lower California at Thurloe Head, 

 Santa Maria Bay, and Magdalena Bay, 17 to 40 fms; Gulf of Califor- 

 nia at Carmen Island, Georges Island, Lobos Point, Tortuga Island, 

 Angel de la Guardia Island, and Tiburon Island, shore to 25 fms; 

 Isabel Island, north of White Friars Islands, and Tangola Tangola 

 Bay, Mexico, 10 to 25 fms; Salinas Bay, Costa Rica, 1.5 to 6 fms; 

 Secas Islands, Panama, 5 to 20 fms ; Port Utria and off Gorgona Island, 

 Colombia, 15 to 30 fms. 



Ampelisca pacifica Holmes 

 Plates 21 and 22 



Ampelisca pacifica Holmes (1908), Proc. U.S. Natl. Mus., vol. 35, no. 

 1654, pp. 511-513, figs. 20-22. 



Description of female: Head nearly as long as first 3 body segments, 

 anterior margin incised, lower front margin subparallel to upper margin. 

 Upper pair of eyes near front margin of head, lower pair at inferoante- 

 rior angle of head. 



Antenna 1 reaching middle of fifth article of antenna 2 peduncle; 

 article 1 tumid, article 2 slightly more than twice as long as first, article 

 3 subequal to 1 in length. 



Antenna 2 more than three fourths as long as body; article 5 of 

 peduncle about two thirds as long as article 4. 



Mandible : spine row with 9 spines ; article 3 of palp more than two 

 thirds as long as article 2. 



Maxilla 1 : outer plate with 1 1 spines ; article 2 of palp large, apex 

 with 5 spines, 4 cusp teeth, and 15 setae. 



